All of lore.kernel.org
 help / color / mirror / Atom feed
From: Anna-Maria Gleixner <anna-maria@linutronix.de>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Luiz Capitulino <lcapitulino@redhat.com>,
	Haris Okanovic <haris.okanovic@ni.com>
Subject: Re: [patch 0/3] do not raise timer softirq unconditionally (spinlockless version)
Date: Wed, 29 May 2019 16:52:37 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1905291651500.1395@somnus> (raw)
In-Reply-To: <20190415201213.600254019@amt.cnet>

Hi,

I had a look at the queue and have several questions about your
implementation. 

First of all, I had some troubles to understand your commit messages. So I
first had to read the code and then tried to understand the commit
messages. It is easier, if it works the other way round.

On Mon, 15 Apr 2019, Marcelo Tosatti wrote:

> For isolated CPUs, we'd like to skip awakening ktimersoftd
> (the switch to and then back from ktimersoftd takes 10us in
> virtualized environments, in addition to other OS overhead,
> which exceeds telco requirements for packet forwarding for
> 5G) from the sched tick.

You would like to prevent raising the timer softirq in general from the
sched tick for isolated CPUs? Or you would like to prevent raising the
timer softirq if no pending timer is available?

Nevertheless, this change is not PREEMPT_RT specific. It is a NOHZ
dependand change. So it would be nice, if the queue is against
mainline. But please correct me, if I'm wrong.

[...]

> This patchset reduces cyclictest latency from 25us to 14us
> on my testbox. 
> 

A lot of information is missing: How does your environment looks like for
this test, what is your workload,...?

Did you also run other tests?

Thanks,

	Anna-Maria

  parent reply	other threads:[~2019-05-29 14:52 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-15 20:12 [patch 0/3] do not raise timer softirq unconditionally (spinlockless version) Marcelo Tosatti
2019-04-15 20:12 ` [patch 1/3] timers: raise timer softirq on __mod_timer/add_timer_on Marcelo Tosatti
2019-05-29 14:53   ` Anna-Maria Gleixner
2019-05-30 19:23     ` Marcelo Tosatti
2019-04-15 20:12 ` [patch 2/3] timers: do not raise softirq unconditionally (spinlockless version) Marcelo Tosatti
2019-05-29 14:53   ` Anna-Maria Gleixner
2019-05-30 20:14     ` Marcelo Tosatti
2019-05-31 11:55       ` Anna-Maria Gleixner
2019-06-11 11:45         ` Anna-Maria Gleixner
2019-06-04  6:29   ` Peter Xu
2019-06-06 15:14     ` Marcelo Tosatti
2019-04-15 20:12 ` [patch 3/3] timers: condense pending bitmap information Marcelo Tosatti
2019-04-15 20:17 ` [patch 0/3] do not raise timer softirq unconditionally (spinlockless version) Marcelo Tosatti
2019-05-06  3:22 ` Marcelo Tosatti
2019-05-06  7:17   ` Daniel Bristot de Oliveira
2019-05-06  9:22   ` Thomas Gleixner
2019-05-29 14:52 ` Anna-Maria Gleixner [this message]
2019-05-30 19:38   ` Marcelo Tosatti

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=alpine.DEB.2.21.1905291651500.1395@somnus \
    --to=anna-maria@linutronix.de \
    --cc=bristot@redhat.com \
    --cc=haris.okanovic@ni.com \
    --cc=lcapitulino@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-rt-users@vger.kernel.org \
    --cc=mtosatti@redhat.com \
    --cc=tglx@linutronix.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.